The apocalypse imagined by David Macaulay in Motel of the Mysteries: Through a programming glitch, the 3rd-Class mailing rate is accidentally set to zero, and the US is buried under several hundred feet of junk mail in an instant.

Mayan calenders, Fah! Wimpy asteroids, I laugh ! I predicted last year that the world would end when the Texas Rangers play the Chicago cubs in the World series. (No one could fault my almost Scalzi-like logic.)
So we only have about ten thousand years left, people. Let’s get busy here with the little amount of time we have remaining.

What? silly birds? Why, no, of course, the Vogons show up! Or some other alien race we can’t deal with, and the first person they kill? Will Smith. Because, well, he kicked the tail of two different alien races, and we can’t have that, now, can we?

What is this “movie” of which you speak? Oops! was that my out loud voice? Damn. Lord Vark won’t be happy.

Deprived of my deeply insightful comments, the Internet devolves even further into a wretched hive of spam and villainy. When the Singularity awakens the Internet, it is so twisted and evil that the Universe OS crashes, and all die.

If the question is “when will the world end for all humans”, I think the general theory is that in a billion or so years, as the sun increases in brightness, the Earth’s oceans will start to dry up. The process will take a while, but human’s will probably cease to be able to breathe and drink water in about 2 billion years from now.

Took me ages to track it down, since the title is so unhelpfully similar to a John Le Carre spy book and to something I’d never heard of until today that is apparently a popular modern revisionist take on Alice in Wonderland. But anyway, turns out it was called The Looking Glass War, it’s by Brandan Dubois, it’s on the Baen anthology you can find at http://www.webscription.net/p-168-future-weapons-of-war.aspx and it’s pretty much about the world coming to an end (or in this case, about America being conquered) because everyone got addicted to Angry Birds and forgot to wash.

I liked a lot of the alternatives — but that’s just it, this was a “pick one” question, not a “pick all.” But I’ve figured out that the cat answer is always best. If we all just pick the cat answer, things will go well.

Some say the world will end in fluff;
Some say in cats.
Because I know a lot of stuff
I hold with those who favor fluff.
But if there were too many rats,
I think I know enough of claws
To say that for destruction cats
Have fewer flaws
And win their spats.

Likelier but less exciting answer for the latter. Civilization as we know it gradually crumbles from peak oil and climate change, leaving human comparatively helpless, and after many centuries, our descendents die out, or lose sentience.

Less likely is everything turns to gray goo because of runaway nanotech.

I hope I’m not the only one who didn’t know that their are two lists of answers- Here,
and at polldaddy.
Penultimately, I suppose the world will end in fire as I run out of hemorrhoid
cream as the sun expands into a red dwarf or whatever, and ultimately into
nothing as the quantum fluctuation that brought everything into being (just to tick off
classical physics;) by ignoring that e=mc… thing unflucts.